Alien Disequilibrium: The Unmistakable Signal of Biological Life
What if an alien civilization was a billion or more years older than ours and detected Earth in its early history? “For billions of years of Earth history, an alien astronomer may have even been sufficiently misled to conclude that Earth was sterile—despite the fact that life was flourishing in our ocean at the time,” says Stephanie Olson, an astrobiologist at the University of California, Riverside with NASA’s Astrobiology Institute.
If we know the past as we can see what’s happened how do we not know what other civilizations see?